Electrical wires generally contain an inner metal conductor surrounded by an insulation material. The insulation becomes more brittle with age, and can crack or develop defects due to age, heat, exposure to strong electrical fields, and friction with other wires or surrounding objects or surfaces. Problems in electrical wiring systems are an important threat to the safety of spacecraft and aircraft, as well as other electrical devices. An electrical short in power bus wiring shortly after takeoff of Space Shuttle mission STS-93 resulted in loss of redundant main engine controller function. Arcing wire was blamed for the catastrophic losses of TWA Flight 800 and SwissAir Flight 111.
Polyimides are high performance polymers that have been used as wire insulation in demanding applications that have low tolerance for failure, such as space travel and aeronautics. The standard wire insulation for spacecraft and aircraft is polyimide, particularly KAPTON. Polyimides have excellent thermal stability and strength. Many hours are also expended in the repair and inspection of electrical wiring in an attempt to prevent wire failure.
Wire insulation with a built in self-healing capability would improve the safety of systems containing electrical wiring. Such insulation would require less inspection and repair time over the lifetime of the system.
All engineered materials eventually fail. They then must be replaced or repaired. A goal of this work is new self-healing materials that will repair themselves when they are damaged. An identified use for these new high performance self-healing materials is self-healing wire insulation. This would reduce the need for manual wire insulation repair and replacement and reduce the risk of failures, such as electrical shorts, that can result in loss of life.
A second area where self-healing would be desirable is inflatable structures, both terrestrial and space applications. Inflatable habitats are planned for use in space exploration. Inflatable habitats face risks of damage and puncture from micrometeroids and orbital debris externally, as well as potentially internally from movement of persons and equipment inside the structure. The ability to heal and seal an inflatable structure to prevent gas escape or to stop gas escape quickly after a puncture happens is a high priority. Of course, any material that could self heal in an inflatable barrier in space would also have uses in inflatable structures on earth, as well as in other types of structures.
New self-healing materials are needed for uses that include wire insulation, healing polyimides, especially aromatic polyimides, and healing inflatable structures to stop or prevent gas leakage.